Pulmonary angiography

Pulmonary angiography

1. Pulmonary angiography and its application Dr.Pankaj Kaira JR-I Radiodiagnosis SRMSIMS, Bareilly India

2. Purpose Describe the techniques used to improve the quality of MD-CTPA Illustrate the diagnostic criteria of chronic and acute pulmonary emboli Illustrate common artifacts and pitfalls in imaging and diagnosis

3. Pulmonary Embolism Pulmonary embolism is the third most common acute cardiovascular disease after myocardial infarction and stroke and results in thousands of deaths each year because it often goes undetected .

4. Diagnostic tests for thromboembolic disease include (a) the D- dimer assay, which has a high sensitivity but poor specificity in this setting (b) ventilation-perfusion scintigraphy , which has a high sensitivity but very poor specificity and (c) lower limb ultrasonography , which has a high specificity but low sensitivity . (CT) pulmonary angiography is becoming the standard of care for the evaluation of patients with suspected pulmonary embolism

5. Imaging Tests for Detection

6. CTPA Godwin et all in 1980 were the first to describe pulmonary embolism on contrast-enhanced CT CTPA has now become the test of choice and de facto standard of care Thin slice MD-CTA has been shown in recent studies to have a sensitivity of 90-100% and specificity of 89-94%, using angiography as the gold standard

7. CTPA, how we do it Pt. lies supine, with arms up 80-100cc Optiray 370 (370 mgI/ml) is injected into antecubital vein using 18 or 20g iv. Injection rate 4cc/sec Test bolus 20cc at 4cc/sec Scan delay = time to peak + 5 seconds – Usually 20-25 seconds Total scan time for typical pt under 10 seconds

8. Parameter Value Number of Acquisitions 1 Oral Contrast None First Acquisition Landmarks Thoracic inlet to lowest diaphragm IV Contrast yes Volume 60 cc Injection Rate 4.0mL/sec Dual Injection yes, 30mL normal saline chase Timing Bolus Main PA, using 10mL contrast Delay time to peak + 5 seconds Slice thickness 0.625mm Pitch 1.375 Table speed 27.5 Reconstruction interval 0.625mm Noise index 11.57 Algorithm standard Reconstruction coronal, axial 10mm MIPS; 2.5mm lung and standard

9. Diagnostic Criteria of Acute PE Complete arterial occlusion with failure to opacify vessel lumen. Artery may be enlarged as compared to others of the same order Central filling defect surrounded by contrast producing the “polo mint” sign on images acquired perpendicular to the long axis of a vessel and the “railway track” sign on longitudinal images of the vessel Peripheral intraluminal filling defect that makes an acute angle with the arterial wall

10. Acute PE Acute angles

11. Peripheral wedge-shaped areas of hyperattenuation that may represent infarcts, along with linear bands, have been demonstrated to be statistically significant ancillary findings associated with acute pulmonary embolism. However, these radiologic features are not specific for pulmonary embolism. If findings in the pulmonary arteries are indeterminate and the lungs are clear, ventilation-perfusion scintigraphy may be performed.

12. Right Sided Heart Failure RV dilatation with or without contrast reflux into the hepatic veins Deviation of the interventricular septum toward the LV Pulmonary embolism index greater than 60% Right ventricular strain or failure is optimally monitored with echocardiography.

13. Diagnostic Criterial for Chronic PE Complete occlusion of vessel that is smaller than others of same order of branching Peripheral crescent shaped intraluminal filling defect that makes obtuse angles with the vessel wall Contrast flowing through vessels that appear thick-walled often smaller arteries due to recanalization A web or flap within a contrast material–filled artery S econdary signs, including extensive bronchial or other systemic collateral vessels, an accompanying mosaic perfusion pattern , or calcification within eccentric vessel thickening

14. Chronic PE Obtuse angles

15. Causes of Misdiagnosis of PE Patient-related Factors. Respiratory Motion Artifact. Image Noise. Pulmonary Artery Catheter. Flow-related Artifact. Technical Factors. Window Settings. Streak Artifact. Lung Algorithm Artifact. Partial Volume Artifact. Stair Step Artifact. Anatomic Factors. Partial Volume Averaging Effect in Lymph Nodes. Vascular Bifurcation. Misidentification of Veins. Pathologic Factors. Mucus Plug. Perivascular Edema. Localized Increase in Vascular Resistance. Pulmonary Artery Stump In Situ Thrombosis. Primary Pulmonary Artery Sarcoma. Tumor Emboli.

16. Artifacts, Image Quality and the Indeterminate CTPA

17. Respiratory Motion Artifact Respiratory motion artifacts are the most common cause of indeterminate CT pulmonary angiography and can cause misdiagnosis of pulmonary embolism. These artifacts are best seen with lung window settings and can create the “seagull” sign Image inferior to superior Avoid exaggerated hyperventilation techniques Technologist training Less of an issue with quick MD-CTPA techniques

18. Flow related artifact : Bilateral lower lobe flow-related artifacts due to poor mixture of blood and contrast material can cause transient interruption of contrast enhancement. Transient interruption of contrast enhancement is likely related to inspiration and to unenhanced blood entering the right atrium, right ventricle, and pulmonary arteries from the inferior vena cava just prior to image acquisition. A flow-related artifact can be confidently diagnosed by identifying its ill-defined margins and by demonstrating an attenuation level above 78 HU. As CT scanners become faster, delaying initial image acquisition until approximately 5 seconds after inspiration should allow the transient interruption in contrast material to pass through the pulmonary circulation

19. Flow Artifacts • • • Transient interruption of flow-column of contrast agent due to increased unopacified blood flow from IVC Interface between high and low attenuation areas ill- defined Limit pre-scan hyperventilation techniques

20. Flow artifacts - other causes Localized increase in vascular resistance – Atelectasis, consolidation Focal slow flow may mimic PE Similar appearance to other flow artifacts

21. Timing of Bolus High injection rate (4cc/sec) with uniphase injection bolus preferred method . This allows a high intensity of contrast enhancement in the pulmonary arterial system. Two components; first pass and recirculation First pass optimized by concentration of iodine (370mg I/mL) Recirculation depends on injection duration

22. Timing • If an indeterminate scans still occurs due to poor enhancement and there is no contrast extravasation and the timing was adequately compensated, there then is likely poor venous flow from stenosis or obstruction – We consider repeat CTPA after hydration or another test

23. Image Noise Images obtained in large patients have more quantum mottle. Image noise makes the evaluation of segmental and subsegmental vessels difficult and can cause indeterminate CT pulmonary angiography and misdiagnosis of pulmonary embolism

24. Body Habitus Image noise Increase radiation dose Increase reconstruction width to 2.5mm Contrast volume May need to increase volume in patients over 250lbs to adequately opacify pulmonary arteries (up to 130mL of 370mg I/mL).

25. Streak Artifacts Contrast column in SVC may cause attenuation artifacts in subsegmental pulmonary arteries Proper timing with added recirculation effect, saline chasers ameliorate this effect

26. Lung Algorithm Artifact The lung algorithm A high-spatial-frequency reconstruction convolution kernel Used to improve the quality of images of the pulmonary vessels, bronchi, and interstitium . This algorithm can create image artifacts that appear similar to pulmonary emboli. However, these artifacts can be removed with a standard algorithm

27. Stair step artifact Stair step artifact consists of low-attenuation lines seen traversing a vessel on coronal and sagittal reformatted images and is accentuated by cardiac and respiratory motion. This artifact can be eliminated or reduced by reconstructing the raw data with a 50% overlap prior to three-dimensional image reconstruction.

28. Stair step artifact

29. Partial Volume Averaging affect in Lymph Nodes Hilar lymph nodes : upper lobe, interlobe , middle lobe ( lingular ), and lower lobe groups. The location of lymph nodes are varies among patients. With a 1.25-mm detector width, lymphatic tissue can be more easily distinguished from PE than 5 mm detector width. Lymphatic tissue is extramural lesion. The review of sagittal and coronal reformatted images can help in difficult cases.

30. Partial Volume Averaging affect in Lymph Nodes

31. Vascular Bifurcations On axial images, vascular bifurcations may simulate linear filling defects . Sagittal and coronal reformatted images can help identify these normal anatomic structures.

32. Vascular Bifurcations

33. Misidentification of Veins False filling defects may be demonstrated within the pulmonary veins. Generally, arteries course adjacent to the corresponding bronchi, with the exception of the apical-posterior segment of the left upper lobe and the lingular arteries.

34. Misidentification of Veins CT scan shows unenhanced pulmonary veins (arrows), which can mimic complete occlusive pulmonary embolism. However, this pitfall can be recognized by observing veins on contiguous images to the level of the right atrium.

35. Mucus Plug A mucus plug within a bronchus, which may also demonstrate peripheral wall enhancement related to inflammation, can mimic acute pulmonary embolism. In addition, viewing the bronchus on contiguous images will demonstrate the true nature of the artifact.

36. Mucus Plug

37. Perivascular Edema Peribrochovascular interstitial thickening from heart failure can mimics PE. Accompanying CT findings in heart failure Diffuse ground-glass attenuation Interlobular septal thickening Diffuse peribronchovascular interstitial thickening Bilateral pleural effusions.

38. Perivascular Edema Left-sided heart failure in a 56-year-old woman with dyspnea . (a) CT scan shows peribronchovascular interstitial thickening caused by perivascular edema (arrow), a finding that can mimic chronic pulmonary embolism. (b) CT scan (lung window) demonstrates the accompanying findings of diffuse peribronchovascular thickening , ground-glass attenuation , smooth interlobular septal thickening (arrows), and bilateral pleural effusions . These findings indicate the true nature of the patient’s condition.

39. Localised increase in Vascular resistance A focal increase in vascular resistance from consolidation or atelectasis . The unenhanced vessel may be normal The poor contrast enhancement may obscure thrombus. A region of-interest measurement may be helpful if the attenuation is greater than 78 HU. Further imaging may be necessary, consisting of either repeat CT pulmonary angiography with an increased delay or pulmonary angiography.

40. Localised increase in Vascular resistance

41. Pulmonary Artery Stump Insitu Thrombus Intravascular thrombosis can identified in a pulmonary artery stump. The criteria for in situ thrombus include Thrombus at the surgical site only. Absence of other pulmonary artery thrombi remote from the stump site.

42. Pulmonary artery stump in situ thrombosis in a 69-year-old man who had undergone right pneumonectomy for lung cancer. CT scan demonstrates pulmonary artery stump in situ thrombosis that affects the right pulmonary artery (arrow). Pulmonary Artery Stump Insitu Thrombus

43. Primary Pulmonary Artery Sarcoma Primary pulmonary artery sarcoma An uncommon cause of an intraluminal arterial filling defect. Unilateral, lobulated , heterogeneously enhancing masses at CT. May demonstrate vascular distention and local extravascular spread. Acute angle and enhancement.

44. Primary Pulmonary Artery Sarcoma Pulmonary artery sarcoma in a 65-year old woman with dyspnea . Contrast-enhanced CT scan shows a heterogeneously enhancing, lobulated mass within the main pulmonary artery (arrow). A metastatic deposit is noted within the right pulmonary artery (arrowhead).

45. Tumor Emboli In a review of microscopic pulmonary tumor emboli associated with dyspnea , Kane et al found that Most common causes: CA prostate and CA breast. Followed by hepatoma , CA stomach and pancreas.

46. Tumor Emboli Manifestations of tumor emboli at CT include Large emboli in the main, lobar, and segmental pulmonary arteries, mimic PE . Small tumor emboli that affect subsegmental arteries and produce vascular dilatation and beading that increases in size over time Small tumor emboli that affect secondary pulmonary lobule arterioles and have a tree-in-bud appearance .

47. Tumor Emboli Common : small tumor emboli leading to progressive dyspnea and subacute pulmonary HT. Rare : larged tumor emboli.

48. Tumor Emboli Tumor embolus in a 78-year-old woman with dyspnea and endometrial stromal sarcoma that invaded the inferior vena cava. CT scan shows a large tumor embolus within the right lower lobe pulmonary artery (arrow).

49. Tumor Emboli Tumor emboli in a 60-year-old man with dyspnea and primary renal cell carcinoma. vascular dilatation and beading of subsegmental arteries tree-in-bud appearance

50. The Indeterminate CTPA Reasons? Can they be resolved with a repeat CTPA with appropriate modifications to the protocol? Level? To what level is the study indeterminate? If subsegmental and clinical pretest probability low, further imaging may not be required. Consider U/S, V/Q or pulmonary angiography

51. Conclusions CTPA has become the test of choice and de facto standard of care for diagnosis of PE Diagnostic criteria for the appearance of acute and chronic clot are well established The indeterminate CTPA study can be limited with proper technique and an understanding of common imaging pitfalls and artifacts

52. Thank You